| A pulsar is a celestial body with extreme physical conditions such as ultra-high density,super electromagnetic field and super gravitational field.Pulsar rotation is extremely stable and radiates electromagnetic pulse signals with obvious characteristics outward.In particular,millisecond pulsars have a rotation rate of 10-19 to 10-21s/s and an long-term stability of10-15.It is comparable to the most stable atomic clock and is known as the most accurate astronomical clock in nature.Long-term high-precision time observation of a group of millisecond pulsars can build a highly stable pulsar time system and define a new time reference-pulsar time.The pulsar time scale can change the pattern of the current time service relying solely on the atomic time,and can also improve the long-term stability of the atomic time scale.Based on this,this paper mainly carried out the research on the construction method of pulsar timing and pulsar time scale.Pulsar high-precision timing data processing is an important basis for carrying out pulsar scientific research and engineering applications.The thesis studies the pulsar timing observation principle and timing model fitting process.The 13-year data for PSR J0437-4715by the release of the Parkes Pulsar Time Array is processed.Using multi-backends fusion processing algorithm,through singular value decomposition and least squares fitting,the device delay between observation backends is determined and eliminated,the timing accuracy is improved,and the parameters of the pulsar timing model are updated.In addition,the effects of different solar-system ephemeris and pulsar parameter errors on the fitting of the timing model are analyzed.For timing residuals containing related timing noise,the Cholesky spectrum analysis method was studied.An analytical model of noise is built on the observation data of PSR J0437-4715 to estimate the frequency spectrum of timing noise,and the timing residual is whitened by the covariance of timing residuals.The timing accuracy has been significantly improved.At the same time,more accurate estimates of pulsar timing model parameters and errors have been obtained.The position and proper motion have also been significantly improved,with the accuracy of right ascension and declination improved by 45?as and 20?as respectively.The accuracy of proper motion in RA and proper motion in DEC are improved by 0.1?as·yr-1 and 1.2?as·yr-1.The pulsar time scale is a new time reference,which is based on the macroscopic motion of dense celestial bodies.In this paper,we study the algorithm of establishing ensemble pulsar time Scale by global least squares fitting.Using Cholesky and Bayesian estimation methods to process the timing data of 8 millisecond pulsars in the international pulsar timing array IPTA DR2,a new ensemble pulsar time Scale TT(EPT)is established based on the global least squares fitting algorithm.The results show that the ensemble pulsar time Scale shows the same stability as TT(BIPM2016)and can monitor the fluctuations of TT(TAI).Finally,the effect of a single millisecond pulsar on the integrated pulsar time is discussed.It is found that the contribution of the integrated pulsar time mainly comes from a few millisecond pulsars with long observation time and high quality observation(PSR J1713+0747,PSR J0437-4715,PSR J1909-3744). |
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